Geosynthetics - Geotechnical Investigation and Design Tables - page 207

Table 16.7 Robustness required for ground conditions and construction equipment (Austroads, 1990).

Ground conditions Robustness for construction equipment

ground pressures

Natural ground clearance Depressions and

humps

Low Medium High

( 25 kPa) (25-50 kPa) ( 50 kPa)

< >

Clear all obstacles except 150 mm in depth Slightly Moderate to Very robust

<

grass, weeds, leaves and and height. Fill any robust robust (2,000-3,000)

fine wood debris larger depressions (600-900) (900-2,000)

Remove obstacles larger 450 mm in depth Moderate to Very robust Extremely

<

than small to moderate and height. Fill any robust (2,000-3,000) robust

sized tree limbs and rocks larger depressions (900-2,000) ( 3,000) >

Minimal site preparation. over tree trunks, Very robust Extremely Not

Trees felled and left in depressions, holes, (2,000-3,000) robust recommended

place. Stumps cut to no and boulders ( 3,000) >

more than 150 mm above
ground

16.8 Geotextile durability for cover material and
construction equipment

•

The table above was based on 150mm to 300mm initial lift thickness for the
cover material.

•

The size, angularity and thickness of the cover material also affect the G - Rating
Requirement.

•

For Pre-rutting increase robustness by one level.

Table 16.8 Robustness for cover material and construction equipment (modified from Austroads,
1990).

Ground conditions Robustness for construction equipment

Ground pressures (kPa)and lift thickness (mm)

Cover Material Low Medium High Medium High

material shape ( 25 kPa) (25-50 kPa) ( 50 kPa) (25-50 kPa) ( 50 kPa)

< > >

150-300 mm 300-450 mm

>

450 mm 150-300 mm 300-450 mm

Fine sand to Rounded to Slightly robust Moderately to robust

±

50 mm gravel subangular (600-900) (900-2,000)

Coarse gravel May be Moderate to robust Very robust

with diameter angular (900-2,000) (2,000-3,000)

up to ½
proposed lift
thickness
Some to most Angular and Very robust Extremely robust

aggregate

>

½ sharp-edged, (2,000-3,000) (

>

3,000)

proposed lift few fines

thickness